How lithium-ion batteries work

Almost all smartphones these days are powered by lithium-ion batteries. And recently, they’ve gotten some special attention, thanks to the type of batteries causing a fire inside Galaxy Note 7 phones. Of course, not all lithium-ion batteries are going to cause fires like that, as it’s highly dependent on the manufacturing process. Still, it makes you wonder: how do lithium-ion batteries work exactly?

There’s quite a bit that goes into them, so we’re going to show you how they work as well as some advantages and disadvantages of using lithium-ion batteries in phones. All of this information isn’t necessary to memorize and retain, but it’s still worth knowing a little about the type of battery that powers our smartphones and tablets — some of the devices that we use day-in and day-out.

Join us after the break for details!

How they work

Lithium-ion batteries are made out of a power generating compartment (or multiple compartments). This is more technical language, but they’re commonly referred to as cells. A cell (or compartment) usually has three components inside: both a positive and negative electrode, connected to the battery’s “+” and “-” terminals, respectively. Sitting in-between these two electrodes is a chemical called an electrolyte (also known as a separator).

The positive electrode is sort-of where the lithium-ion battery gets its name from, as this electrode is usually constructed out of lithium-cobalt oxide. On the other hand, the negative electrode is typically made out of a carbon material, typically carbon. As for the electrolyte itself, the material can vary from battery to battery.

What’s particularly important in the construction of lithium-ion batteries is the type of metal used. Since the battery is pressurized, the metal casing has to have some sort of vent hole. If the battery gets too hot from pressure, the vent hole will release some of that pressure. Now, in either case, the battery is fried and unusable after that, so the vent hole is more of a safety mechanism in order to prevent harm to the user.

But, what’s particularly interesting about lithium-ion batteries is how they charge. They’re built with a computer, or electronic controller that regulates or determines how the battery is charged or discharged. This electronic controller is vital. If you think about it, we usually plug our phones in the night by either our nightstand or somewhere else. Now, it doesn’t take all night to charge a battery, so one of the components that prevents the battery from being overcharged (and even overheated) is that electronic controller.

So, how do lithium-ion batteries charge and discharge exactly? During the charging process, lithium ions move from the positive electrode, through the electrolyte (or separator) and into the negative electrode. What’s also critical to the charging process are electronics. These don’t flow the same way lithium ions do. Instead, they take a different path around the circuit. But, together, both ions and electrons combine together in the negative electrode and deposit lithium. When ions won’t flow anymore (usually regulated by the electronic controller), the battery isn’t going to charge anymore — this, generally, means that the battery is charged and ready to use!

Now, how a battery is discharged is essentially the opposite. All of the ions and electrons that moved to the negative electrode all travel back to the positive electrode. In the same way, ions flow through the separator and the electrons take another path around the circuit, until they both meet at the positive electrode, depositing lithium, and ultimately, powering your smartphone or another gadget that uses a lithium-ion battery. When all the lithium is moved into the positive electrode (from the negative electrode) your battery has been depleted and needs recharging. From there, we start the same process all over again to get a proper charge.

Advantages of lithium-ion

There are a lot of great advantages of lithium-ion batteries. For example, with smartphones and tablets, we need to charge them quite frequently — pretty much daily. Lithium-ion batteries are able to easily handle this load, as they are able to handles hundreds upon hundreds of charge and discharge cycles. Other types of batteries can handle similar loads, but could deteriorate faster after every charge/discharge cycle.

Another neat thing about lithium-ion batteries is that their battery chemistry is made up in a way that they have no memory effect. In other words, you don’t have to completely discharge a lithium-ion battery in order to start charging it up again. In addition to that, lithium-ion batteries are able to hold a charge extremely well. If you’re not using it, you may only experience a 5% discharge per month, whereas a NiHM (nickel-metal hydride) battery can experience as much as a 20% discharge per month.

Lithium-ion batteries are also much more lightweight than other rechargeable batteries. This is largely because they’re made of lightweight lithium (as the name implies) as well as carbon. Additionally, lithium-ion batteries also have a high energy density because of how reactive lithium is. In other words, a single lithium-ion battery can store up to 150 watt hours of electricity in just 1kg of battery. So, as you can see, the capacity possibilities are quite high, especially as we reap the benefits of Research & Development efforts.

…but there are also the disadvantages

While there are a plethora of advantages that come with lithium-ion batteries, there are some flaws, too. One of those flaws is that lithium-ion batteries start degrading the minute they get off the line at the factory. Wondering why your battery dies every two to three years? Because lithium-ion batteries don’t last much longer than that, whether you’re using them or not. That’s some of the frustration behind manufacturers closing off access to the back of the device. Once the battery dies, you’re almost forced to get a replacement since many batteries are no longer removable, as they have been in the past.

Another negative is the lithium-ion battery’s sensitivity to temperatures. In normal or mild temperatures, the battery will operate without a hitch. Lithium-ion batteries can’t handle extreme heat or extreme cold. According to a report published by Battery University, cold temperature “increases the internal resistance and lowers the capacity.”

Here’s what they have to say on that:

“As all drivers in cold countries know, a warm battery cranks the car engine better than a cold one. Cold temperature increases the internal resistance and lowers the capacity. A battery that provides 100 percent capacity at 27°C (80°F) will typically deliver only 50 percent at –18°C (0°F). The momentary capacity-decrease differs with battery chemistry.”

Their performance in hotter temperatures isn’t that great either:

“All batteries achieve optimum service life if used at 20°C (68°F) or slightly below. If, for example, a battery operates at 30°C (86°F) instead of a more moderate lower room temperature, the cycle life is reduced by 20 percent. At 40°C (104°F), the loss jumps to a whopping 40 percent, and if charged and discharged at 45°C (113°F), the cycle life is only half of what can be expected if used at 20°C (68°F).”

The good news is that freezing temperatures isn’t going to have any long-term affect on your battery. In the moment, you may notice that you go from 30% or 50% battery to dead, but you won’t be suffering any long-term damage; however, in extreme heat, you will experience wear to the life cycle, as outlined above.

Those are the major disadvantages. There are some other minor ones. For instance, there needs to be an on-board computer to manage the battery, potentially making lithium-ion batteries more expensive. There’s also a slight chance that, when a lithium-ion battery fails, it will burst into flames; however, that’s a rare scenario.

Closing

And that wraps up our quick look at the lithium-ion battery. There’s quite a bit of technology that goes into these batteries, and it’s quite interesting how they keep getting smaller and smaller, but still allowing for a larger battery capacity. There’s plenty of advantages to the lithium-ion battery, too. And while there are a few disappointing disadvantages, for the most part, the benefits these types of batteries bring to the table outweigh those disadvantages.

Things will only improve with lithium-ion batteries as companies start reaping the benefits of Research & Development efforts as well. From here on out, we’ll be seeing some very specialty manufacturing processes, allowing these type of batteries to have an even thinner profile all while either increasing the capacity or making them much more efficient than previous renditions. It goes without saying, what we’ll be seeing in the future is going to be extremely technical, but also an amazing work of technology.

Brad is a tech enthusiast, writing and tinkering with all things technology since 2011. He currently bounces between the LG G3 and his beloved Moto X! His interests include reading, entrepreneurship, the gym, and of course, queso.